SiC (silicon carbide) is expected to be a material for next-generation power semiconductor devices. SiC has excellent physical properties, having a band gap three times wider than that of Si (silicon), a breakdown field strength approximately 10 times higher than that of Si, and a heat conductivity approximately three times higher than that of Si. A power semiconductor device that has low loss and is capable of high-temperature operation can be realized by taking advantage of those properties.
However, in a power semiconductor module such as a voltage-type power conversion module, the problem of device breakdown due to overshoot voltage at turn-off becomes serious is switching operation becomes faster. The overshoot voltage at turn-off is proportional to the time rate (di/dt) of change in the current flowing in the circuit.
If the switching period is made longer so as to suppress overshoot, the switching operation becomes slower. Also, switching loss, which is expressed by the time integral of a product of current and voltage (∫ixvxdt), becomes larger. So as to suppress overshoot and reduce switching loss, the parasitic inductance of the power semiconductor module should be reduced.